Effect of Geometry and Gate Voltage on the Conductance of an Ideal Strip of Graphene

Abstract

One of the enormous challenges in the transistor fabrication industry is to find materials with suitable electronic properties. On the other hand, the size of electronic systems is being reduced every day. Therefore, flexibility and suitable electronic properties are required simultaneously. Graphene is a perfect example of a two dimensional (2D) electronic transport system that shows resilience, as it is a very specific one-atom thick structure that has surprising metallic electronic properties. In this report, I have simplified the mode-dependent transmission probability of Dirac fermions in an ideal graphene nanoribbon (length L, width W, and no impurities), to determine the conductance as a function of the Fermi energy in the channel. The conductance results presented in this project are based on two main components (a) geometry, and (b) chemical potential variation in the channel (gate voltage). First by setting the gate voltage to zero, the effect of altering the geometry (aspect ratio between W and L), on the conductance is evaluated. Then the chemical potential (gate voltage) is changed while keeping the geometry fixed. Finally, the physical relationship between the chemical potential and gate voltage in a field effect transistor (FET) channel is examined, and the connection between the conductance and gate voltage for a range of aspect ratios is assessed. Performance results are presented which show that the conductance of a narrow and wide graphene strips has a universal minimum value (quantum conductance), at the Dirac point (gate voltage equal to zero), which is an important criterion in achieving a ballistic channel.